Dogwood tree- `Rutlan`

ABSTRACT

An F 1  hybrid of Cornus kousa Hance and C. florida L. providing a new large-bracted dogwood, which is an exceptionally vigorous, highly floriferous, small, flowering tree, more nearly like C. florida, being full and spreading in habit rather than vase-shaped as in C. kousa, yet considerably larger as compared with C. florida, and having a period of floral display that is intermediate to that of the parental species.

BACKGROUND OF THE DISCLOSURE

This invention relates to a large-bracted dogwood cultivar, which is oneof those developed in an extensive program of interspecifichybridization, in an effort to produce characteristics which aredesirable in dogwood trees and the results have justified my efforts Ibelieve.

The particular cultivar hereof, as one of a series of dogwood treesresulting from an extensive period of development, embodiescharacteristics which make the same commercially attractive and therebyhaving substantial potential for commercial distribution.

The interspecific hybridization in this instance is that of an unnamedseedling of Cornus kousa and a plant of Cornus florida known as`Hillenmeyer` which is unpatented.

Some of the characteristics which I have provided as a result of myprogram, and which this particular cultivar exhibits, include a tall,spreading habit and a much larger tree than certain low, spreadingplants of which a companion plant Cornus×`Rutfan` (U.S. Plant Pat. No.7,206) is exemplary. Other plants developed generally during the sameperiod of time are more erect in habit and differ in possessing floralbracts of different size, shape, texture, and/or color.

This particular cultivar, is one of a group which will be referred to ingeneral and in some instances, specifically, by comparison foridentification and other purposes.

The instant cultivar which I have chosen to designate for commercialidentification as `Rutlan`, is one of a number of dogwood cultivarswhich I have developed, and it is compared herein with certain of theothers which are also designated by their commercial names, and plantpatent numbers where applicable.

It will be understood that the parental species C. florida and C. kousahave been used as a basis for the cultivars referred to and thus many ofthe characteristics will be found as common, yet each in turn isdistinctive in its own way.

I note that plants of this species combination have not been reportedpreviously, by anyone other than myself.

Field plantings of the instant cultivar `Rutlan` in the vicinity of NewBrunswick, N.J., do not reveal infestation by the dogwood borer nor havethey exhibited "dogwood decline."

I am thus of the opinion that the plant `Rutlan`, hereof may be grownwherever plants of the parental species C. florida and/or C. kousa aregrown and will exhibit the desirable characteristics and distinctionsset forth herein.

In comparison with the upright habit of `Rutban`, (U.S. Plant Pat. No.7,205) `Rutdan`, (U.S. Plant Pat. No. 7,204) and `Rutgan`, (U.S. PlantPat. No. 7,207), plants of `Rutlan` are spreading in habit, flowerearlier, have a distinctly lower number of true flowers per flower head,and exhibit floral bracts that do not overlap; in addition, the floralbracts of `Rutlan` provide a white floral display in the spring incontrast with the bracts of `Rutgan` which provide a spring floraldisplay of pink bracts. The plant form of `Rutlan` is wider than tall incontrast with the erect (taller than wide) form of `Rutcan`, (U.S. PlantPat. No. 7,210) in addition, the floral display of `Rutlan` typicallybegins two days earlier than that of `Rutcan`; also the white floralbracts of `Rutlan` are shorter and wider than those of `Rutcan`. Thefloral display of `Rutlan` typically starts only one day earlier thanthat of `Rutfan` (U.S. Plant Pat. No. 7,206) and the number of trueflowers per flower head in these two hybrids is quite similar; however,plants of `Rutlan` are much larger and exhibit a height/width ratio thatis higher than that for plants of `Rutfan` (approximately 0.82 versus0.58); furthermore, the foliar bracts of `Rutlan` are longer and widerthan those of `Rutfan`.

My new hybrid is highly sterile.

In order to summarize the various characteristics which are notable inmy new cultivar, I have broken down the aspects of the same regardingtree shape, flower buds, bracts and other characteristics which will beset forth hereinafter in the specific succinct summaries noted below.

I have caused the cultivar of my new dogwood tree to be reproducedasexually by grafting, budding or rooting of stem cuttings and foundthat it retains its distinguishing characteristics from generation togeneration.

When color is referred to, The Royal Horticultural Society Colour Chartis availed of and the colors are as nearly true as is possible to makethe same in an illustration of this character, made by photographicmeans.

In the drawing

FIG. 1 shows a somewhat enlarged view of floral bracts.

FIG. 2 shows a tree in full bloom so to speak.

Tree: Plant erect as a very young specimen but is vigorous and spreadingso it soon develops a form that is densely branched and foliaged closeto the ground such that the tree appears full and spreading throughoutits entire height; at the end of its 19th growing season, the originalseedling had attained a height of 5.5 meters (18 feet) and a uniformspread of 6.7 meters (22 feet). Very floriferous but non-productive astree is highly sterile; typically a regular bearer but there is sometendency toward alternate bearing, as the floral display is somewhatdiminished the year following an unusually heavy floral display.

Hardy.--In U.S.D.A. Plant Hardiness Zone 6a (-5 degrees to -10 degreesF.).

Trunk: Medium size; but becoming shaggy with age, as then exhibitsexfoliating bark.

Branches: Medium; smooth.

Lenticels: Numerous, medium.

Leaves: Abundant.

Length.--9.0-14.3 cm (average=11.60).

Width.--4.2-6.8 cm (average=5.4) at widest point; i.e., slightly longerand wider than those of the C. kousa parent and slightly shorter andnarrower than those of the C. florida parent.

Shape.--Elliptic; acuminate tip; base broadly cuneate, often mildlyoblique; margin very mildly undulate;

Color.--Dark green: color varies slightly during the growing season;upper surface observed to be 137A or 139A (R.H.S. Color Chart -- GreenGroup); lower surface 138B (Green Group) or 191A (Greyed Green Group).

Petioles:

Length.--8-16 mm (average 12.2 mm).

Flower buds: (The true flowers are small and numerous and are borne inflower heads. They are relatively inconspicuous. The floral display isprovided by large floral bracts that subtend the flower heads. In commonterminology and often in the art, the floral bracts are described asthough they were the flowers.) Medium size (larger than those of C.kousa but smaller than those of C. florida); plump; covered with lightbrown pubescence. Over winter, the lower pair of vegetative bracts onthe peduncle extend to the base of the flower head or slightly higher;the upper pair of bracts loosely enclose the true flowers and extendnearly to the tip of the flower head but do not tightly enclose the trueflowers. The four floral bracts do not overlap at all and there isconsiderable variability (20 to 45% of the true flowers are exposed)from flower head to flower head in the degree to which the true flowersare enclosed by the four floral bracts and the uppermost pair ofvegetative bracts. Hence, some of the exposed true flowers maywinterkill during an unusually cold winter in U.S.D.A. Plant HardinessZone 6a (-5 degrees to -10 degrees F.).

Floral bracts:

Shape.--Round to slightly obovate with a broadly attenuate base and amucronate tip; the individual bracts do not overlap.

    ______________________________________                                        Color:                                                                               Start of   Mid-season  Peak of                                                floral display                                                                           floral disp.                                                                              flor. disp                                      ______________________________________                                        Upper    157B         157C        155A                                        surface  Green-White  Green-White White                                       Lower    157C         157C        155A                                        surface  Green-White  Green-White White                                       ______________________________________                                    

Size.--Intermediate in size to those of typical plants of C. kouse andC. florida. When the floral bracts are fully expanded, the diameter, orspread, of the inflorescence from tip to tip of the opposing innerbracts is about 113 mm; the diameter of the inflorescence as measuredfrom tip to tip of the opposing outer bracts is about 107 mm. Theaverage length of the inner bracts is approximately 55 mm; the averagelength of the outer bracts is approximately 52.5 mm. The average widthof the inner bracts at their widest point is 39 mm; the average width ofthe outer bracts at their widest point is 41 mm. Bract length and widthmay show considerable variation from year to year, but the inner bractstypically are longer and narrower than the outer bracts.

Peduncle length.--Each flower head is borne on a peduncle, the averagelength of which has been found to be approximately 4.2 cm at the time offlowering. Absolute peduncle length varies from year to year, but thepeduncle length of this hybrid will typically be found to beintermediate to that of plants of the parental clones.

Flowers: The period of floral display (floral bracts) is basicallyintermediate to that of plants of the parent species; i.e., occurs inearly-to-mid May, commencing two to three days prior to the completionof the floral display of late-flowering specimens of C. florida andceasing several days prior to the start of the floral display of typicalplants of C. kousa. Anthesis of the tiny, relatively inconspicuous, trueflowers generally commences two to four days following the onset of theornamental display of the large, floral bracts and ceases a few daysprior to the end of the period of floral display. Thus, the period ofpollen release seldom overlaps that of plants of either parent species.The average number of true flowers per flower head of this new hybrid isapproximately 31.

Fruit: Fully developed fruit have not been observed, as plants of thisnew interspecific hybrid are highly sterile. However, a few flower headsmay persist for a month or two and exhibit some parthenocarpicdevelopment, or enlargement. However, there is no formation of a syncarpas in C. kousa, as the flowers in this new hybrid are distinct andseparate in the flower head, or on the receptacle.

Insects: In field plantings with C. kousa and C. florida, Dogwood Borershave ravaged plants of C. florida, but have not infested plants of mynew F₁ interspecific hybrid.

Diseases: In field plantings with C. florida and C. kousa, my new F₁interspecific hybrid has made vigorous growth and remained in goodhealth whereas many plants of C. florida have died as a result of the"dogwood decline" that has decimated cultivated and wild stands of C.florida in the East in recent years.

I claim:
 1. A new and distinct cultivar of dogwood tree, substantiallyas herein shown and described, characterized particularly as to noveltyby the unique combination of its exceptionally high vigor and highlyfloriferous small flowering form, similar to its pollen parent as to itsdense, spreading form but becoming much taller with age, intermediate tothe two parents as to characteristics of the overwintering flower buds,time of flowering, and size of floral bracts, and exhibiting resistanceto dogwood borers and "dogwood decline."